Improving quality of service in the internet

The Internet transport technology was designed to be robust, resilient to link or node outages, and with no single point of failure. The resulting connectionless system supports what is called a "best effort datagram delivery service", the perfo rmance of which is often greatly unpredictable. To improve the predictability of IP-based networks, several Quality of Service technologies have been designed over the past decade. The first one, RSVP, based on reservation of resources, is operational but has several major deficiencies, such as scalability difficulties. However, associated to other more recent technologies -RSVP aggregation, Diffserv and MPLS- the combination may result into an appropriate solution for improving Quality of Service guarant ees in a scalable way. This article presents the state of the art on the field in an accurate, yet pedagogical style